The Central Nervous System (CNS) is composed of the brain and the spinal cord. The CNS is utilized to scan, evaluate and process, and respond to the information we receive primarily through our sense organs.
The spinal cord is primarily used for motor functions of skin, joints, muscles, and ligaments and conveying motor commands for movements. A spinal nerve contains afferent fibers which enter the spinal cord and are specifically used to carry the information to the spinal cord and efferent fibers which exit the spinal cord and are specifically used to carry the information from the spinal cord to the organs.
The brainstem contains the cell bodies—the nuclei of the nerve cells of the cerebellum. It is composed of three parts: first medulla is the lower part which connects the brainstem to the spinal cord. The second (above medulla) pons (or the bridge) whose nerve cells connect to the cerebral cortex and to the cerebellum. The third part of the brainstem is the midbrain which is situated over the pons.
The cerebellum is the control center for the motor functions. It involves coordination of the range and force of movements and posture.
The diencephalon contains the thalamus and hypothalamus. The thalamus is an important switchboard for all afferent sensory input except for the sense of smell. The hypothalamus resides under the thalamus and is the center for autonomic activities.
Above the hypothalamus sits a reservoir of nerve centers called the limbic system where both inborn and acquired behavior are regulated.
The cerebral hemispheres are divided by sucli or grooves into four parts: the frontal, parietal, temporal, and occipital lobes. The two hemispheres are connected to each other by the corpus cullosum. Each of the hemispheres is the center for specialized types of functions.
The frontal lobe is primarily concerned with complex motor functions including movement. The prefrontal fibers reside in the forward portion of the frontal lobe, and are concerned with control of actions to conform to social moves. The primary sensory cortex is located in the parietal lobe. The temporal lobe is concerned with one's hearing, memory and sense of time, and plays a role in human emotional experiences. The occipital lobe is the specialized center for visual experiences.
The left hemisphere of the brain works in an interpretive way. It operates analytically, breaking the received data into their most elementary constituents, then studying each element one by one. This leads to exaggerations and deviations from the realistic path.
The right hemisphere of the brain is concerned with perceptual aspects of stimuli. This results in a more literal picture than obtained from the left brain.
Some psychologists believe that every person has two types of minds; the objective mind and the subjective mind.
Neurophysiologal observations indicate that the functions of the brain are intimately related to the number of communicating neurons and their interconnections.
Each neuron is comprised of a nucleus, a long fiber called the axon, and a varying number of branching fibers called dendrites, which extend out to other neurons.
There are about 10 synapses in the human brain. A single neuron can make numerous contacts.
Every new thought process is handled by a new set of synaptic connections. Memory itself is a set of synaptic connections engraved in the network of neurons.
A nerve cell responds to a stimulus by changing the electrical properties of its cell membrane. In its unexcited state, an electric potential difference exists across the membrane of a living cell. Stimuli increases the positive ion concentration of the outer membrane, to increase the magnitude of the potential difference, called depolarization.